Circuit structure and fabrication method thereof

ABSTRACT

A circuit structure is provided, which includes a plurality of conductive posts, and a plurality of first and second conductive pads formed on two opposite end surfaces of the conductive posts, respectively. A length of each of the first conductive pads is greater than a width of the first conductive pad so as to reduce an occupation area of the first conductive pad along the width and increase a distance between adjacent first conductive pads, thereby increasing the wiring density and meeting the wiring demand.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to circuit structures and fabricationmethods thereof, and more particularly, to a circuit structure and afabrication method thereof for meeting the miniaturization requirement.

2. Description of Related Art

Along with the rapid development of electronic industries, electronicproducts are required to be much lighter, thinner, shorter and smallerand multi-functional. Accordingly, there have been developed varioustypes of semiconductor packages and various types of packagingsubstrates for disposing semiconductor chips. For example, circuitstructures can be provided for packaging substrates by using MIS (moldedinterconnect system) packaging technologies.

FIGS. 1A to 1C are schematic cross-sectional views showing a method forfabricating a circuit structure 1 by using MIS packaging technologies.

Referring to FIGS. 1A and 1A′, a plurality of circuits 16, 17, aplurality of first conductive pads 11 and a plurality of conductiveposts 13 are sequentially formed on a surface 10 a of a carrier 10. Eachof the first conductive pads 11 has a circular shape. Each of theconductive posts 13 has a cylindrical shape. Then, an encapsulant 14 isformed on the surface 10 a of the carrier 10 by molding forencapsulating the first conductive pads 11 and the conductive posts 13.Further, surfaces of the conductive posts 13 are exposed from theencapsulant 14.

Referring to FIGS. 1B and 1B′, a plurality of circuits 16, 17 are formedon the encapsulant 14 and a plurality of second conductive pads 12 areformed on the exposed surfaces of the conductive posts 13 and theencapsulant 14 around peripheries of the conductive posts 13. Each ofthe second conductive pads 12 has a circular shape.

Referring to FIG. 1C, the carrier 10 is removed to expose the firstconductive pads 11 from the encapsulant 14. As such, a circuit structure1 is formed. The first and second conductive pads 11, 12 can be used forbonding with solder bumps and solder balls, respectively. Further, eachof the conductive posts 13 has a diameter r and each of the first andsecond conductive pads 11, 12 has a diameter d greater than the diameterr.

However, in the conventional circuit structure 1, since the first andsecond conductive pads 11, 12 are circular-shaped metal pads and occupya certain area of the overall wiring space, the wiring of the circuits16, 17 is limited. For example, a certain distance must be kept betweenthe circuits 17 and the first conductive pads 11, and consequently, onlya limited number of the circuits 17 can be formed to pass between twoadjacent first conductive pads 11, thereby adversely affecting thewiring flexibility, reducing the wiring density and making it difficultto meet the demands for fine-pitch and multi-joints.

Further, since the diameter d of each of the first and second conductivepads 11, 12 is greater than the diameter r of each of the conductiveposts 13, the conductive posts 13 have a smaller-sized path of thermaland electrical conduction compared with the first and second conductivepads 11, 12, thus leading to poor thermal and electrical conductivitiesof the circuit structure 1.

Therefore, how to overcome the above-described drawbacks has becomecritical.

SUMMARY OF THE INVENTION

In view of the above-described drawbacks, the present invention providesa circuit structure, which comprises: a plurality of conductive postseach having opposite first and second end surfaces; a plurality of firstconductive pads bonded to the first end surfaces of the conductiveposts, wherein a length of each of the first conductive pads is greaterthan a width of the first conductive pad; and a plurality of secondconductive pads bonded to the second end surfaces of the conductiveposts.

The present invention further provides a method for fabricating acircuit structure, which comprises the steps of: forming a plurality offirst conductive pads on a carrier, wherein a length of each of thefirst conductive pads is greater than a width of the first conductivepad; forming a plurality of conductive posts on the first conductivepads, wherein each of the conductive posts has opposite first and secondend surfaces and the first conductive pads are bonded to the first endsurfaces of the conductive posts; and forming a plurality of secondconductive pads on the second end surfaces of the conductive posts.

After forming the second conductive pads, the above-described method canfurther comprise removing the carrier.

In the above-described structure and method, each of the firstconductive pads has a polygonal shape or an asymmetric geometric shape.For example, each of the first conductive pads has a quadrilateral shapeor a rounded elongated shape.

In the above-described structure and method, each of the firstconductive pads is less in area than the first end surface of thecorresponding conductive post.

In the above-described structure and method, a length of each of thesecond conducive pads is greater than a width of the second conductivepad. For example, each of the second conductive pads has a polygonalshape or an asymmetric geometric shape. In particular, each of thesecond conductive pads has a quadrilateral shape or a rounded elongatedshape.

In the above-described structure and method, each of the secondconductive pads is less in area than the second end surface of thecorresponding conductive post.

After forming the conductive posts, the method can further compriseforming an insulating layer on the carrier for encapsulating theconductive posts. For example, the insulating layer is an encapsulant.The insulating layer can further encapsulate the first conductive pads.In an embodiment, the second conductive pads are formed first and thenthe insulating layer is formed to encapsulate the second conductivepads. In another embodiment, the insulating layer is formed before thesecond conductive pads are formed.

According to the present invention, the length of each of the firstconductive pads is greater than the width of the first conductive pad soas to reduce an occupation area of the first conductive pad along anaxial direction and increase a distance between adjacent firstconductive pads. As such, the wiring space is increased. For example,the number of circuits passing between two adjacent first conductivepads is increased. Therefore, the present invention increases the wiringdensity and meets the demands for fine-pitch and multijoints.

Further, since each of the first and second conductive pads can be lessin area than the end surface of the corresponding conductive post, theconductive post has a larger-sized path of thermal and electricalconduction relative to the first and second conductive pads. As such,the circuit structure of the present invention achieves preferredthermal and electrical conductivities.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1C are schematic cross-sectional views showing a method forfabricating a circuit structure according to the prior art, wherein FIG.1A′ is a partially upper view of FIG. 1A, and FIG. 1B′ is a perspectiveview of the circuit structure (not including an encapsulant);

FIGS. 2A to 2F are schematic cross-sectional views showing a method forfabricating a circuit structure according to the present invention,wherein FIG. 2A′ is an upper view of FIG. 2A, FIG. 2D′ shows anotherembodiment of FIG. 2D, and FIGS. 2F′ and 2F″ show other embodiments ofFIG. 2F;

FIGS. 3A to 3C are schematic perspective views showing differentembodiments of the circuit structure of the present invention; and

FIGS. 4 and 4′ are schematic cross-sectional views showing a method forfabricating a circuit structure according to another embodiment of thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following illustrative embodiments are provided to illustrate thedisclosure of the present invention, these and other advantages andeffects can be apparent to those in the art after reading thisspecification.

It should be noted that all the drawings are not intended to limit thepresent invention. Various modifications and variations can be madewithout departing from the spirit of the present invention. Further,terms such as “first”, “second”, “on”, “a” etc. are merely forillustrative purposes and should not be construed to limit the scope ofthe present invention.

FIGS. 2A to 2F are schematic cross-sectional views showing a method forfabricating a circuit structure 2 according to the present invention.

Referring to FIGS. 2A and 2A′, a patterned first metal layer is formedon a carrier 20. The first metal layer has a plurality of circuits 26,27 and a plurality of first conductive pads 21 connected to the circuits26.

In the present embodiment, each of the first conductive pads 21 has alength Y and a width X and the length Y is greater than the width X. Assuch, the first conductive pad 21 has a rounded elongated shape, forexample, an oval shape. Therefore, an occupation area of the firstconductive pad 21 along an axial direction (i.e., the width X direction)is reduced and a distance between adjacent first conductive pads 21 isincreased, thereby increasing the wiring space. For example, comparedwith the prior art that only allows one circuit to pass between twoadjacent conductive pads, the present invention allows a plurality ofcircuits 27 (for example, three circuits) to pass between two adjacentfirst conductive pads 21.

In other embodiments, referring to FIGS. 3A to 3C, each of the firstconductive pads 31, 31′, 31″ has a polygonal shape, for example, aquadrilateral shape or a rounded elongated shape, or an asymmetricgeometric shape, for example, a T-shape or a curved shape.

Further, referring to FIG. 3C, the first conductive pad 31″ serves asboth a heat dissipating pad and a power source pad. Therefore, a chip(not shown) only needs a single electrode pad to be electricallyconnected to the first conductive pad 31″.

Referring to FIG. 2B, a first photoresist layer 28 a is formed on thecarrier 20 for encapsulating the first conductive pads 21, and surfacesof the first conductive pads 21 are exposed from the first photoresistlayer 28 a. Then, a second photoresist layer 28 b is formed on the firstphotoresist layer 28 a. The second photoresist layer 28 b has aplurality of open areas 280 corresponding in position to the firstconductive pads 21 so as to expose the surfaces of first conductive pads21.

Referring to FIG. 2C, a plurality of conductive posts 23 are formed onthe first conductive pads 21 in the open areas 280. Each of theconductive posts 23 has a first end surface 23 a and a second endsurface 23 b opposite to the first end surface 23 a. The firstconductive pads 21 are bonded to the first end surfaces 23 a of theconductive posts 23.

In the present embodiment, the conductive posts 23 are copper cylinders.An area A of each of the first conductive pads 21 is less than an area Bof the first end surface 23 a of the corresponding conductive post 23.Therefore, the conductive post 23 has a larger-sized path of thermal andelectrical conduction compared with the first conductive pad 21, therebyimproving heat dissipation and electrical conduction effects of theconductive post 23.

Referring to FIGS. 3A to 3C, each of the first conductive pads 31, 31′,31″ of different shapes is less in area than the first end surface 33 aof the corresponding conductive post 33.

Referring to FIGS. 2D and 3A, a patterned second metal layer is formedon the second end surfaces 23 b of the conductive posts 23. The secondmetal layer has a plurality of circuits 26, 27 and a plurality of secondconductive pads 22, 32 connected to the circuits 26 and bonded to thesecond end surfaces 23 b of the conductive posts 23.

In the present embodiment, referring to FIG. 2D and FIGS. 3A to 3C, thesecond conductive pads 22, 32, 32′, 32″ have a shape similar to thefirst conductive pads 21, 31, 31′, 31″. For example, each of the secondconductive pads has a polygonal shape, for example, a quadrilateralshape or a rounded elongated shape, or an asymmetric geometric shape.

An area C of each of the second conductive pads 22 is less than the areaB of the second end surface 23 b of the corresponding conductive post23. In another embodiment, referring to FIG. 2D′, an area C′ of each ofthe second conductive pads 22′ is greater than the area B of the secondend surface 23 b of the corresponding conductive post 23.

Referring to FIG. 2E, continued from FIG. 2D, the first and secondphotoresist layers 28 a, 28 b are removed and then a molding process isperformed to form an insulating layer 24, such as an encapsulant, on thecarrier 20. The insulating layer 24 encapsulates the first conductivepads 21, the conductive posts 23 and the second conductive pads 22. Inthe present embodiment, the insulating layer 24 has opposite first andsecond sides 24 a, 24 b. The first conductive pads 21 are positioned atthe first side 24 a of the insulating layer 24. The conductive posts 23are positioned in the insulating layer 24. The second conductive pads 22are positioned at the second side 24 b of the insulating layer 24.

Further, the first conductive pads 21 are embedded in the first side 24a of the insulating layer 24 and the second conductive pads 22 areembedded in the second side 24 b of the insulating layer 24.

Referring to FIG. 2F, the carrier 20 is removed to expose the firstconductive pads 21 from the first side 24 a of the insulating layer 24.

In another embodiment, referring to FIG. 2F′, a circuit structure 2′ isformed according to the process of FIG. 2D′.

Referring to FIG. 2F″, the first and second photoresist layers 28 a, 28b are removed first and then a molding process is performed. Thereafter,a plurality of second conductive pads 22″ are formed on the second endsurfaces 23 b of the conductive posts 23 and positioned on the secondside 24 b of the insulating layer 24.

According to the present invention, the length Y of each of the firstconductive pads 21 is greater than the width X of the first conductivepad 21 so as to reduce an occupation area of the first conductive pad 21along an axial direction and increase a distance between adjacent firstconductive pads 21. Therefore, the present invention increases thewiring space and density and meets the wiring demand

Similarly, an occupation area of each of the second conductive pads 22along an axial direction can be reduced to achieve the same effect. Forexample, a plurality of circuits 27 (for example, two circuits) areallowed to pass between two adjacent second conductive pads 22 in FIG.2F, while only one circuit 27 is allowed to pass between two adjacentsecond conductive pads 22′ in FIG. 2F′.

Further, the area A of each of the first conductive pads 21 is less thanthe area B of the first end surface 23 a of the corresponding conductivepost 23. In addition, the area C of each of the second conductive pads22 can be less than the area B of the second end surface 23 b of thecorresponding conductive post 23. As such, the conductive post 23 has alarger-sized path of thermal and electrical conduction relative to thefirst and second conductive pads 21, 22. Therefore, the circuitstructure 2 has preferred thermal and electrical conductivities.

In an embodiment, referring to FIG. 4, first, the second photoresistlayer 28 b is removed and the second conductive pads 22′ and theinsulating layer 24 are formed. Then, the first photoresist layer 28 aand the carrier 20 are removed. As such, the first conductive pads 41are positioned on the first side 24 a of the insulating layer 24.

In another embodiment, referring to FIG. 4′, a support member 29 isfurther disposed on the first side 24 a of the insulating layer 24. Forexample, a hard member is provided after the carrier 20 is removed, orthe support member 29 is directly fabricated from the carrier 20.

The present invention further provides a circuit structure 2, 2′, 2″, 3,3′, 3″, 4, 4′, which has: a plurality of conductive posts 23, 33 eachhaving opposite first and second end surfaces 23 a, 23 b; a plurality offirst conductive pads 21, 31, 31′, 31″ bonded to the first end surfaces23 a of the conductive posts 23, 33, wherein a length Y of each of thefirst conductive pads 21, 31, 31′, 31″ is greater than a width X of thefirst conductive pad 21, 31, 31′, 31″; and a plurality of secondconductive pads 22, 22′, 22″, 32, 32′, 32″ bonded to the second endsurfaces 23 b of the conductive posts 23, 33.

Each of the first conductive pads 21, 31, 31′, 31″ can have aquadrilateral shape, a rounded elongated shape (for example, an ovalshape) or an asymmetric geometric shape (for example, a T-shape).

A length of each of the second conductive pads 22, 22′, 22″, 32, 32′,32″ can be greater than a width of the second conductive pad 22, 22′,22″, 32, 32′, 32″. For example, each of the second conductive pads 22,22′, 22″, 32, 32′, 32″ has a polygonal shape or an asymmetric geometricshape (for example, a T-shape).

In an embodiment, an area A of each of the first conductive pads 21, 31,31′, 31″ is less than an area B of the first end surface 23 a of thecorresponding conductive post 23.

In an embodiment, an area C of each of the second conductive pads 22 isless than an area B of the second end surface 23 b of the correspondingconductive post 23.

In an embodiment, the circuit structure 2, 2′, 2″, 4, 4′ further has aninsulating layer 24, for example, an encapsulant. The insulating layer24 has opposite first and second sides 24 a, 24 b. The first conductivepads 21 are embedded in the first side 24 a of the insulating layer 24.The conductive posts 23 are positioned in the insulating layer 24. Thesecond conductive pads 22″ are positioned on the second side 24 b of theinsulating layer 24. Alternatively, the second conductive pads 22, 22′are embedded in the second side 24 b of the insulating layer 24.

According to the present invention, the length of each of the conductivepads can be greater than the width of the conductive pad so as to reducean occupation area of the conductive pad along an axial direction andincrease a distance between adjacent conductive pads. Therefore, thepresent invention increases the wiring space and density and meets thedemands for fine-pitch and multi-joints.

Further, since each of the conductive pads can be less in area than theend surface of the corresponding conductive post, the conductive posthas a larger-sized path of thermal and electrical conduction comparedwith the conductive pad. As such, the circuit structure of the presentinvention achieves preferred thermal and electrical conductivities.

The above-described descriptions of the detailed embodiments are only toillustrate the preferred implementation according to the presentinvention, and it is not to limit the scope of the present invention.Accordingly, all modifications and variations completed by those withordinary skill in the art should fall within the scope of presentinvention defined by the appended claims.

What is claimed is:
 1. A circuit structure, comprising: a plurality ofconductive posts each having opposite first and second end surfaces; aplurality of first conductive pads bonded to the first end surfaces ofthe conductive posts, wherein a length of each of the first conductivepads is greater than a width of the first conductive pad; and aplurality of second conductive pads bonded to the second end surfaces ofthe conductive posts.
 2. The structure of claim 1, wherein each of thefirst conductive pads has a polygonal shape or an asymmetric geometricshape.
 3. The structure of claim 2, wherein each of the first conductivepads has a quadrilateral shape or a rounded elongated shape.
 4. Thestructure of claim 1, wherein each of the first conductive pads is lessin area than the first end surface of the corresponding conductive post.5. The structure of claim 1, wherein a length of each of the secondconducive pads is greater than a width of the second conductive pad. 6.The structure of claim 1, wherein each of the second conductive pads hasa polygonal shape or an asymmetric geometric shape.
 7. The structure ofclaim 6, wherein each of the second conductive pads has a quadrilateralshape or a rounded elongated shape.
 8. The structure of claim 1, whereineach of the second conductive pads is less in area than the second endsurface of the corresponding conductive post.
 9. The structure of claim1, further comprising an insulating layer encapsulating the conductiveposts, wherein the insulating layer has opposite first and second sides,the first conductive pads being positioned at the first side of theinsulating layer and the second conductive pads being positioned at thesecond side of the insulating layer.
 10. A method for fabricating acircuit structure, comprising the steps of: forming a plurality of firstconductive pads on a carrier, wherein a length of each of the firstconductive pads is greater than a width of the first conductive pad;forming a plurality of conductive posts on the first conductive pads,wherein each of the conductive posts has opposite first and second endsurfaces and the first conductive pads are bonded to the first endsurfaces of the conductive posts; and forming a plurality of secondconductive pads on the second end surfaces of the conductive posts. 11.The method of claim 10, wherein each of the first conductive pads has apolygonal shape or an asymmetric geometric shape.
 12. The method ofclaim 11, wherein each of the first conductive pads has a quadrilateralshape or a rounded elongated shape.
 13. The method of claim 10, whereineach of the first conductive pads is less in area than the first endsurface of the corresponding conductive post.
 14. The method of claim10, wherein a length of each of the second conducive pads is greaterthan a width of the second conductive pad.
 15. The method of claim 10,wherein each of the second conductive pads has a polygonal shape or anasymmetric geometric shape.
 16. The method of claim 15, wherein each ofthe second conductive pads has a quadrilateral shape or a roundedelongated shape.
 17. The method of claim 10, wherein each of the secondconductive pads is less in area than the second end surface of thecorresponding conductive post.
 18. The method of claim 10, after formingthe conductive posts, further comprising forming an insulating layer onthe carrier for encapsulating the conductive posts.
 19. The method ofclaim 10, after forming the second conductive pads, further comprisingremoving the carrier.